Glutathione is a peptide consisting of three amino acids, i.e., L-cysteine, L-glutamic acid, and glycine. Glutathione is present in a wide variety of living organisms including not only humans but also other animals, plants, and microorganisms, and it is an important compound for living organisms that is involved in, for example, removal of active oxygen species, detoxification, and amino acid metabolism.
Glutathione is present in vivo in the form of either reduced glutathione (N—(N-γ-L-glutamyl-L-cysteinyl)glycine) in which the thiol group of the L-cysteine residue is reduced in the form of SH (hereafter, it may be referred to as “GSH”) or oxidized glutathione in which the thiol group of the L-cysteine residue is oxidized to form a disulfide bond between two glutathione molecules (hereafter, it may be referred to as “GSSG”).
GSSG is known to be useful in the field of, for example, fertilizers, pharmaceuticals, and cosmetic products.
Patent Document 1 discloses that GSSG is useful as an active component of a plant growth regulator that increases the harvest index. For example, it has activity of increasing the number of seeds and the number of flowers of the plant or increasing the number of lateral shoots or tillers of a plant.
Patent Document 2 discloses that an ammonium salt, a calcium salt, or a magnesium salt of GSSG prepared by the production method under a specific heating condition is low in deliquescence and high in water solubility; that is, such salt is easy to handle.
Meanwhile, Patent Document 3 discloses that, in the presence of glutathione (GSH or GSSG) together with arginine and an organic acid, degradation of glutathione during storage can be inhibited, and storage stability is thus improved.
Patent Document 1: WO 2008/072602
Patent Document 2: WO 2013/002317
Patent Document 3: WO 2009/099132